This invention relates to the preparation of gypsum board and more particularly to improved frothing composition for use in the gypsum dispersions used to make the gypsum board.
In the production of gypsum board a fluid gypsum dispersion is spread between two water impervious barriers such as paper sheet and the resultant composition is heated until the free water has evaporated and the gypsum has set. Because of the weight of gypsum it has become the practice in the industry to incorporate air bubbles into the gypsum core to lower the density of the finished gypsum product. This is accomplished by incorporating a froth or foam into the dispersion prior to the evaporation of water. The froth has been conventionally prepared by agitating an aqueous solution of a frothing agent or composition such as rosin soap. Attempts have been made to utilize in commercial gypsum board manufacturing operations synthetic surfactants such as neutralized sulfonic acids and neutralized sulfuric acid esters. Although these surfactants have been successfully used as detergents in other fields such as in the preparation of dishwshing and clothes washing products, it has been found that the amount and stability of the foam generated by these frothing agents in gypsum slurries was not sufficient to insure uniform low density throughout the gypsum board product. Since neutralized sulfonic acids and sulfuric acid esters are inexpensive and readily available, it would be desirable to use these materials in the manufacture of gypsum board.
U.S. Pat. No. 3,577,248 discloses the use of linear alkyl benzene sulfonates having 8.5 to 10.5 alkyl carbon atoms. This patent also discloses mixtures of sodium xylene sulfonate and C.sub.10 to C.sub.13 linear alkyl benzene sulfonates and mixtures of C.sub.6 to C.sub.7 linear alkyl benzene sulfonates with C.sub.10 -C.sub.13 linear alkyl benzene sulfonates. U.S. Pat. No. 3,512,528 discloses the use of combinations of linear alkyl benzene sulfonates having average alkyl carbon contents of 6 to 15 carbon atoms with certain alcohols, glycols, esters, or ketones.